1. Field of the Invention
The present invention relates to a movable objective lens type optical microscope having a stationary stage and a specimen moving stage and, more particularly, to a movable objective lens type optical microscope which can suitably perform cell manipulation (patch clamp).
2. Description of the Related Art
Cell manipulation (patch clamp) is performed in the field of biology. Patch clamp is executed in electrophysiological experiments of a living cell or tissue or a cultured cell as well as in cell fusion. A movable objective lens type optical microscope having a manipulator, a stationary stage, and a specimen moving stage can be used for performing patch clamp.
FIG. 1 shows a conventional example of an optical microscope of this type. This optical microscope is a vertically movable objective lens type optical microscope on which a manipulator can be mounted and used, as disclosed in Jpn. UM Appln. KOKAI Publication No. 6-4723 (which shows an erect optical microscope). Referring to FIG. 1, the optical microscope has an arm 13 holding a lens barrel, and a base 22, that constitute a frame. The arm 13 is supported on the base 22 such that it can be vertically moved by a linear guide 13A provided between the arm 13 and the base 22.
Focusing knobs 17 for vertically moving the arm 13 are mounted to the arm 13. A stage rest 20 and a lamphouse 23 accommodating a light source are mounted to the base 22. A lens barrel 16 is fixed to the arm 13, and an eyepiece is mounted to its upper distal end. A revolver 15 is rotatably held by the arm 13. A plurality of objective lenses 14 having different magnifications are mounted to the revolver 15 so that an objective lens having a desired magnification can be selectively used.
The plurality of objective lenses 14 having different magnifications are fixed to the revolver 15 by screwing. In accordance with the switching operation of the revolver 15, one of the plurality of objective lenses 14 is set on an optical axis 13B, thereby changing the magnification. The objective lens 14 which is selected upon switching the revolver 15 is paired with the eyepiece, thus constituting the observation optical system of the microscope.
The stage rest 20 is provided upright on the base 22. A cross-moving stage 18 that can be moved in the X and Y directions is a stage for placing a specimen thereon. An end portion of the cross-moving stage 18 is supported by the stage rest 20 so that it is arranged at a position to cross the optical path of the observation optical system on the objective lens 14 side. A window for assuring the optical path is formed at the central portion of the cross-moving stage 18. A condenser rest 21 supports a condenser lens 19 which guides illumination light to the specimen, and is movable vertically. A stationary stage 11 arranged above the cross-moving stage 18 has a window for assuring the optical path at its central portion. The stationary stage 11 is fixed on the base 22 and its front and rear end sides are supported by support plates 24 and 25. A manipulator 12 is used for patch clamp in biological experiments. The manipulator 12 (not shown) can be fixed on the stationary stage 11 with magnets, screws, or the like (not shown).
To perform observation by using such a conventional optical microscope, the power switch of the lamphouse 23 is turned on to light the light source in the lamphouse 23. A specimen is placed on the cross-moving stage 18 in advance. The focusing knobs 17 are rotated to move the objective lenses 14 downward, thus performing focusing. The condenser lens 19 is adjusted at an optimum position by vertically moving the condenser rest 21 through operation of the position adjusting knob.
When a cell to be manipulated is found by observation, the manipulator 12 is set on the stationary stage 11. As the objective lens 14 interferes with this setting operation, it is moved upward. In patch clamp, the cell is fixed by suction or the like (this will be referred to as clamp hereinafter). Electrodes for performing the clamp are integrally formed on the distal end portion of the manipulator 12. These electrodes are set close to the cell.
Thereafter, the objective lens 14 is moved downward again to perform focusing. The electrodes of the manipulator 12 are moved to clamp the cell while observing the cell.
In general, the number of cells to be clamped is about 2 to 4. After one cell is clamped, another manipulator 12 is set on the stationary stage 11 to clamp another cell, and the operation described above is repeated in order to clamp the second cell with the newly set manipulator 12. In this manner, the manipulators 12 corresponding in number to the cells to be clamped are set, and the operation described above is repeated. Then, the experiment is started.
In the conventional microscope described above, when performing an electrophysiological experiment, the manipulator 12 is set on the microscope in order to clamp a cell as a specimen, and thereafter the cell is clamped by operating the manipulator 12. When another cell is to be clamped, a series of operations is repeated in which the objective lens 14 is retreated upward, another manipulator 12 is set and its electrodes are inserted in approximate portions of the cell, and thereafter the objective lens 14 is moved downward.
In this series of operations, a clamped cell may often be easily let loose due to a slight vibration occurring in the operation of setting another manipulator 12. The cell is typically as small as about 5 .mu.m at a minimum, and the support structure for the stationary stage 11 on which the manipulator 12 is set and that for the cross-moving stage 18 for holding the specimen are different and have different vibration systems. Thus, vibrations may occur in the stationary stage 11 and in the cross-moving stage 18 independently of each other.
More specifically, although the conventional cross-moving stage 18 and the stationary stage 11 are both fixed to the base 22 of the microscope, they have arms of different lengths and different support systems, thus having different vibration systems upon application of an external vibration. As a result, the cross-moving stage 18 and the stationary stage 11 do not move in synchronism with each other. When the amplitudes of the vibrations increase, the stationary stage 11 and the cross-moving stage 18 move differently, so that the clamped small cell is undesirably released.
When the conventional optical microscope is examined in the light of the above fact, if the support portions (mounting portions to the base 22) of the stationary stage 11 and the cross-moving stage 18 are narrower than the width between the positions where the focusing knobs 17 are provided, the right-to-left span is excessively short compared to the size of the stationary stage 11, and the stationary stage 11 is thus unstable. In other words, in a microscope, the focusing knobs 17 are respectively mounted to the two sides of the microscope so that they can be operated with both or either one of the two hands. These right and left focusing knobs 17 are mounted to the arm 13 that holds the lens barrel and are comparatively close to the support portions of the stationary stage 11 and the cross-moving stage 18. Hence, to obtain a good operability, the mounting positions of the support portions of the stationary stage 11 and the cross-moving stage 18 must be set such that their widths are smaller than the width between the positions where the right and left focusing knobs 17 are arranged.
The stationary stage 11 and the cross-moving stage 18 have large widths. Accordingly, if the support widths of the stationary stage 11 and the cross-moving stage 18 are small, the stationary stage 11 and the cross-moving stage 18 can easily cause free vibration.
Thus, the stationary stage 11 and the cross-moving stage 18 are accordingly easily influenced by a vibration. In this manner, this support structure is employed in order to avoid interference by the hand when operating the focusing knobs 17. Thus, no problem occurs when operating the focusing knobs 17, as nothing interferes with the hand. However, upon application of an external vibration, the stationary stage 11 and the cross-moving stage 18 cause different vibrations, so that the clamped cell can be easily released.
Assume a case wherein a support structure is employed in which the support portions of the stationary stage 11 and the cross-moving stage 18 are wider than the width between the right and left focusing knobs 17 in order to provide anti-vibration properties against an external vibration. In this case, however, although the anti-vibration properties can be achieved, the operator's hand can easily interfere with the support systems of the stationary stage 11 and the cross-moving stage 18 while operating the focusing knobs 17. Then, the clamped object is released due to the vibration caused by the interference.
The conventional stationary stage 11 has a good stability as it has a sufficient span. However, since the stationary stage 11 and the cross-moving stage 18 have different vibration systems, as described above, when the amplitude of a vibration is large, the clamped object is released.
In summary, in the conventional arrangement, a vibration can be caused easily, and when a vibration occurs, the stationary stage 11 and the cross-moving stage 18 vibrate differently, so that the clamped object can be released easily.
Therefore, the conventional microscope must be handled very carefully and must be operated very prudently. Even then, the clamped object tends to be released, leading to a microscope which is inconvenient to use. Therefore, development of a microscope is demanded in which, during operation of the focusing knobs, the operator's hand will not easily interfere with other constituent elements of the microscope, and the manipulator on the stationary stage will not easily release the clamped object upon application of a vibration.